Regarding possible Cassandra story archs (as I've been overthinking this to high heaven). Here is my wild imagination in action, Sit back and enjoy 
It's a quiet day in Inquistion headquarters when we walk into Cassandra's office/barrack/bedroom...whatever. She claims she has heard news of an intended attack by the Red Templars on a group of former circle mages hiding in a cave system from the conflict and insists that we help them. We ask why she is so concerned by this but she asks us to trust that she has her reasons and to leave the topic alone. But of course this is a choice based game, and we can ignore Cassandras request for a while if we choose, or go immediately. If the former the following plays out:
We arrive to find a massacre, mage bodies are littered everywhere. Cassandra is noticeably distressed, Varric is concerned for her as well as Vivienne but she mostly upset over the needless deaths of the circle mages. We fight through several animated corpse a few demons etc until we come to a large cavern where the largest number of bodies both Templar and mage can be found. the companions state that whatever battle was here is lost but we notice Cassandra grieving over the body of a particular mage. Before anything can be said she drops her sword and leaves the caves. Just as we go to follow one of those big red rocky thing with the arm-hammers(name please??) come in an we have to fight it and a few stray Templars with a party of 3. The battle is done and we return to HQ and to Cassandra's office/bedroom/bedroom, etc to find all her solider kicked out and we can't talk to her/take her on quests for awhile. When we can talk to her she tells us that mage was called Regalyan and the two of them were 'friends'. We can either comfort her or tell her to man up and get back to work.
Option two(going immediately). Go into the caves, Templars everywhere, kill, kill, kill, save the odd mage along the way. Get to the clearing. Mage V Templar battle in progress. Cassandra sees Regalyan, Regalyan sees Cassandra. Slow motion running towards each other whilst avoiding arrows. Okay perhaps not but they are happy to see the other safe(ish) and maybe there is a kiss. Insert witty comment by Varric. Reunion interrupted by big red hammer guy joining the fight. Brief battle, them another cutscence. Galyan notices the seemingly endless influx of Templar and resorts to blood magic (yes I know we're all tired of this scenario but I could thing of no better way to get rid of him with killing him) Cassandra's not happy and he knows this. Return to battle, Galyan is now an ally (of sort) doing much damage to the enemies but using our health to fuel it. We can do nothing but stock up on potions and pray Vivienne is a healer. Eventually the battle is won. Cassandra confront Galyan with her sword to his throat. He apologises but is not angry at her reaction. She say he should die for what he is. INSERT INQUISTOR! we can persuade her to kill him or let him leave with the others but regardless of what we say she throws down her sword and walks away. Depending on the previous dialogue choice we can either warn him or tell him to keep the survivor safe, then we leave for HQ.
Next time we speak to her in her bedroom she is being comforted by Varric (cos I so ship those two). Their conversation ends as we walk in. She apologises for letting personal matters distract her from what the inquistion is about. We can either agree with her or tell her she was right to get us to help those mages. Perhaps the conversation will refer to us convincing her to kill galyan or not, and this will shape her view on mages in the future. Then insert some fantastically written dialogue AND THEN THE ROMANCE BEGINS!!!!!
.....i'll stop thinking now